/*******************************************************************************
 * Copyright (c) 2004, 2005 Elias Volanakis and others.
�* All rights reserved. This program and the accompanying materials
�* are made available under the terms of the Eclipse Public License v1.0
�* which accompanies this distribution, and is available at
�* http://www.eclipse.org/legal/epl-v10.html
�*
�* Contributors:
�*����Elias Volanakis - initial API and implementation
�*******************************************************************************/
package eu.hydrologis.jgrass.formeditor.model;

import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;

import org.eclipse.ui.views.properties.IPropertyDescriptor;
import org.eclipse.ui.views.properties.IPropertySource;

/**
 * Abstract prototype of a model element.
 * <p>This class provides features necessary for all model elements, like:</p>
 * <ul>
 * <li>property-change support (used to notify edit parts of model changes),</li> 
 * <li>property-source support (used to display property values in the Property View) and</li>
 * <li>serialization support (the model hierarchy must be serializable, so that the editor can
 * save and restore a binary representation. You might not need this, if you store the model
 * a non-binary form like XML).</li>
 * </ul>
 * @author Elias Volanakis
 */
public abstract class AModelElement implements IPropertySource, Serializable {
    /** An empty property descriptor. */
    private static final IPropertyDescriptor[] EMPTY_ARRAY = new IPropertyDescriptor[0];

    private static final long serialVersionUID = 1;
    /** Delegate used to implemenent property-change-support. */
    private transient PropertyChangeSupport pcsDelegate = new PropertyChangeSupport(this);

    /** 
     * Attach a non-null PropertyChangeListener to this object.
     * @param l a non-null PropertyChangeListener instance
     * @throws IllegalArgumentException if the parameter is null
     */
    public synchronized void addPropertyChangeListener( PropertyChangeListener l ) {
        if (l == null) {
            throw new IllegalArgumentException();
        }
        pcsDelegate.addPropertyChangeListener(l);
    }

    /** 
     * Report a property change to registered listeners (for example edit parts).
     * @param property the programmatic name of the property that changed
     * @param oldValue the old value of this property
     * @param newValue the new value of this property
     */
    protected void firePropertyChange( String property, Object oldValue, Object newValue ) {
        if (pcsDelegate.hasListeners(property)) {
            pcsDelegate.firePropertyChange(property, oldValue, newValue);
        }
    }

    /**
     * Returns a value for this property source that can be edited in a property sheet.
     * <p>My personal rule of thumb:</p>
     * <ul>
     * <li>model elements should return themselves and</li> 
     * <li>custom IPropertySource implementations (like DimensionPropertySource in the GEF-logic
     * example) should return an editable value.</li>
     * </ul>
     * <p>Override only if necessary.</p>
     * @return this instance
     */
    public Object getEditableValue() {
        return this;
    }

    /**
     * Children should override this. The default implementation returns an empty array.
     */
    public IPropertyDescriptor[] getPropertyDescriptors() {
        return EMPTY_ARRAY;
    }

    /**
     * Children should override this. The default implementation returns null.
     */
    public Object getPropertyValue( Object id ) {
        return null;
    }

    /**
     * Children should override this. The default implementation returns false.
     */
    public boolean isPropertySet( Object id ) {
        return false;
    }

    /** 
     * Deserialization constructor. Initializes transient fields.
     * @see java.io.Serializable
     */
    private void readObject( ObjectInputStream in ) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        pcsDelegate = new PropertyChangeSupport(this);
    }

    /** 
     * Remove a PropertyChangeListener from this component.
     * @param l a PropertyChangeListener instance
     */
    public synchronized void removePropertyChangeListener( PropertyChangeListener l ) {
        if (l != null) {
            pcsDelegate.removePropertyChangeListener(l);
        }
    }

    /**
     * Children should override this. The default implementation does nothing.
     */
    public void resetPropertyValue( Object id ) {
        // do nothing
    }

    /**
     * Children should override this. The default implementation does nothing.
     */
    public void setPropertyValue( Object id, Object value ) {
        // do nothing
    }
}
